The Trump administration’s recent statements and actions have removed any doubt that it is set on dismantling part of the multilateral order which the United States once helped build. America’s retreat from the role of a hegemon that creates and enforces order is a problem for US allies committed to a rule-based world. What can they do to save it, and what can they learn from past episodes of US unilateralism? In this blogpost (based on a new article), we argue that even though great challenges remain, in many policy-areas the prospects of a “multilateralism minus one” have improved.